Water-dispersible polyurethane polymer

ABSTRACT

A water-dispersible polyurethane polymer useful in coating applications preferably includes a backbone having urethane linkages and at least one cycloaliphatic group having a closed aliphatic ring structure. Ethylenically unsaturated groups are preferably provided on the polyurethane polymer.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 13/902,208, filed May 24, 2013, which is adivisional of and claims priority to Ser. No. 11/825,026, filed Jul. 3,2007, which claims priority to U.S. Provisional patent Application No.60/806,593, filed on Jul. 5, 2006, each of which are entitled“WATER-DISPERSIBLE POLYURETHANE POLYMER”, the disclosures of each areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates generally to polyurethane polymers andmore specifically to water-dispersible polyurethane polymers.

BACKGROUND

Coating compositions including polyurethane (PU) polymers generallyexhibit excellent resistance to abrasion, chemicals, and solvents. PUcoatings may be used in various applications such as, for example,coatings for wood, concrete, metal, wood, semi-rigid and flexibleplastics, rubber, leather, glass fiber sizing, printing inks, andadhesives.

PU coating compositions that exhibit suitable mechanical properties forsuch applications may be prepared using oil-modified PU polymers.Conventional oil-modified PU polymers are typically prepared in organicsolvents and applied in clear or pigmented coatings. After applicationof a PU coating composition to a substrate, the organic solvent isevaporated off to form a film that is then typically cured by airoxidation of ethylenic groups included in the PU polymers of the film.

Governments have increasingly established regulations restricting therelease of volatile organic compounds (VOCs) into the atmosphere, whichimpact the use of PU coating compositions containing oil-modified PUpolymers. To reduce the amount of released VOCs, manufacturers have beenreducing the amount of organic solvent in PU coating compositionsthrough use of water-dispersible PU polymers. Conventionalwater-dispersible PU polymers may be produced, for example, by reactingpolyols and dihydroxy carboxylic acid compounds with an excess ofdiisocyanate to provide a carboxy-functional prepolymer havingisocyanate (NCO) terminal groups. The acid groups may be neutralized toprovide a neutralized prepolymer that is dispersible in water, which maybe further modified to elicit various properties.

PU films formed using conventional water-dispersible PU polymerstypically vary from films that are hard and relatively inflexible tofilms that are soft and highly flexible. It is often difficult toprepare a PU film that exhibits a proper blend of performancecharacteristics (e.g., both good hardness and flexibility) fromconventional water-dispersible PU polymers. To achieve both goodhardness and flexibility using conventional water-dispersible PUpolymers, manufacturers typically formulate the PU polymers usingincreased amounts of isocyanate, which may result in increased materialcosts that are prohibitive for various applications.

As such, there is a continuing need for new low VOC or substantiallyVOC-free PU coating systems.

SUMMARY

In one embodiment, the present invention provides a water-dispersible PUpolymer that includes a plurality of urethane linkages, a plurality ofsalt or salt-forming groups, a plurality of air-curable ethylenicallyunsaturated groups, and a plurality of cycloaliphatic groups having thestructure X—Z—X, where Z is an aliphatic ring structure, each X is agroup independently selected from an ester group, an ether group, anamide group, a carbonate group, hydrogen, or CRn, where R isindependently selected from hydrogen, a halogen, oxygen, nitrogen, anorganic group, or a combination thereof and n is 0, 1 or 2, and where atleast one of the X groups is a divalent linkage group that attaches thecycloaliphatic group to another portion of the polyurethane polymer.Preferably, the PU polymer includes at least about 30 weight percent ofthe cycloaliphatic groups and the air-curable ethylenically unsaturatedgroups, based on the total dry weight of the PU polymer.

In another embodiment, the present invention provides a coatingcomposition including the PU polymer described herein and an aqueouscarrier.

In yet another embodiment, the present invention provides a method forforming a PU prepolymer useful for producing the PU polymer of thepresent invention. The PU prepolymer may be neutralized, dispersed in anaqueous carrier, and optionally chain extended.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

Definitions

Unless otherwise specified, the following terms used in thisspecification have the meanings provided below.

The term “cycloaliphatic” refers to an organic compound or groupcontaining a saturated or unsaturated non-aromatic closed ringstructure.

The term “dry weight” as used herein in the context of a prepolymer orpolymer refers to the total weight of the reactants (not including anysolvents) for forming the PU prepolymer or polymer.

The term “isocyanate” refers to organic compounds having at least oneisocyanate, or —NCO, group. Unless indicated otherwise, the termincludes both isocyanates and polyisocyanates (e.g., diisocyanates,triisocyanates, etc.).

The term “prepolymer” refers to an intermediate polymer stage formedduring production of a PU polymer.

The term “organic hydroxyl group” refers to a functional group having ahydroxyl group covalently bonded to a carbon atom, and excludes hydroxylgroups present in carboxylic-functional groups.

The term “water-dispersible” used in the context of a prepolymer (orpolymer) means that (1) the prepolymer is itself capable of beingdispersed into an aqueous carrier such as, for example, water (e.g.,without requiring the use of a separate surfactant) or (2) an aqueouscarrier can be added to the polymer to form a stable dispersion (i.e.,the dispersion should have at least one month shelf stability at normalstorage temperatures). Such water-dispersible polymers can includenonionic or anionic functionality on the polymer, which assist inrendering them water-dispersible. For such polymers, external acids orbases are typically required for anionic stabilization; however, theseare not considered secondary emulsifying agents (e.g., surfactants).

A group that may be the same or different is referred to as being“independently” something. Substitution is anticipated on the organicgroups of the compounds of the present invention. Thus, when the term“group” is used to describe a chemical substituent, the describedchemical material includes the unsubstituted group and that group withO, N, Si, or S atoms, for example, in the chain (as in an alkoxy group)as well as carbonyl groups or other conventional substitution. Forexample, the phrase “alkyl group” is intended to include not only pureopen chain saturated hydrocarbon alkyl substituents, such as methyl,ethyl, propyl, t-butyl, and the like, but also alkyl substituentsbearing further substituents known in the art, such as hydroxy, alkoxy,alkylsulfonyl, halogen atoms, cyano, nitro, amino, carboxyl, etc. Thus,for example, “alkyl group” includes ether groups, haloalkyls,nitroalkyls, carboxyalkyls, hydroxyalkyls, sulfoalkyls, etc.

The terms “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the invention.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a coating composition thatcomprises “an” amine can be interpreted to mean that the coatingcomposition includes “one or more” amines.

DETAILED DESCRIPTION

The present invention provides a polyurethane (PU) polymer for use incoating applications. Preferred PU polymers of the present inventioninclude urethane linkages, cycloaliphatic groups, air-curableethylenically unsaturated groups, and salt groups. If desired, the PUpolymer may be formed via a water-dispersible PU prepolymer intermediatethat may be optionally combined with an aqueous carrier to form adispersion useful in coating applications. The dispersed PU prepolymermay be optionally chain-extended (or otherwise modified or processed) toform a PU polymer useful in coating compositions.

The PU polymer of the present invention may be included in PUdispersions (or coating compositions) for use in a variety of coatingapplications such as, for example, coatings for wood, concrete, metal,semi-rigid and flexible plastics, rubber, leather, glass fiber sizing,printing inks, and adhesives. Due to its water-dispersibility, the PUpolymer of the present invention may be useful in coating applicationsrequiring low or substantially zero VOC levels. Some embodiments of thePU polymer are particularly suited for one-component applications inwood flooring where excellent toughness, chemical and water resistance,and rapid dry times may be required.

As discussed above, to achieve both good hardness and flexibility usingconventional water-dispersible PU polymers, manufacturers typicallyformulate the PU polymers using increased amounts of isocyanate. In someembodiments, PU films prepared using the water-dispersible PU polymer ofthe present invention exhibit both suitable hardness and flexibilitywithout requiring the use of increased isocyanate levels, which mayresult in enhanced cost efficiency. In addition, PU films prepared usingthe water-dispersible PU polymer of the present invention may exhibitenhanced physical properties relative to PU films prepared usingconventional water-dispersible PU polymers. While not wishing to bebound by theory, the cycloaliphatic groups of the PU polymer may enhancethe physical properties of PU films through mobility of the ringstructure, especially when the cycloaliphatic groups are located in abackbone of the PU polymer.

Any suitable cycloaliphatic group may be included in the PU polymer.Examples of suitable cycloaliphatic groups for incorporation in the PUpolymer include groups having the structure X—Z—X, where Z is analiphatic ring structure and each X is a group independently selectedfrom ester groups, ether groups, amide groups, carbonate groups,hydrogen, or CRn, where n is 0, 1 or 2 and R is independently selectedfrom hydrogen, a halogen, oxygen, nitrogen, an organic group, andcombinations thereof (i.e., when n=2, the two R's may be the same ordifferent). One or both of the X groups preferably are linkage groupsthat attach the cycloaliphatic groups to other portions of the PUpolymer.

The structure Z may be any type and/or size of suitable closed aliphaticring structure. For example, Z may be a 3-member organic ring, a4-member organic ring, a 5-member organic ring, a 6-member organic ring,or any other organic non-aromatic aliphatic ring structure having 7 ormore ring members. As used herein the term “n-member ring” (and variantsthereof), where n is an integer, refers to the number n of atoms makingup the ring. In presently preferred embodiments, Z is a six-memberorganic ring structure. Examples of preferred six-member organic ringstructures for Z include cyclohexane groups, cyclohexene groups,cyclohexadiene groups, and variants thereof. In a preferred embodiment,Z is a cyclohexane group having the X groups covalently attached at the1,2; 1,3; or 1,4 positions of the hexane ring.

Cycloaliphatic groups may be incorporated into the PU polymer via anycycloaliphatic-group-containing compound (or combination of compounds).As used herein, the term “cycloaliphatic-group-containing compound”refers to compounds including one or more cycloaliphatic groups of theabove X—Z—X structure, compounds including one or more cycloaliphaticgroups of structures other than the X—Z—X structure, and compoundsincluding both one or more cycloaliphatic groups of the X—Z—X structureand one or more cycloaliphatic groups of structures other than the X—Z—Xstructure. As used herein, when cycloaliphatic-group-containingcompounds used to make the PU polymer are referred to as containing theX—Z—X structure, this refers to compounds that include (1) the entireX—Z—X structure or (2) the Z group and either (i) at least a portion ofthe X groups or (ii) a precursor group used to form at least a portionof the X groups, or (iii) a combination of (i) and (ii).

Examples of suitable cycloaliphatic-group-containing compounds includecycloaliphatic polyols, cycloaliphatic polycarboxylic acids,cycloaliphatic polyesters, cycloaliphatic polyamides, cycloaliphaticalkyd compounds, and combinations thereof. Preferably, at least asubstantial portion (and in some embodiments all) of the cycloaliphaticgroups are provided through compounds including the X—Z—X structure. Insome embodiments, some or all of the cycloaliphatic groups may beincorporated into the PU polymer via cycloaliphatic alkyds and/orcycloaliphatic polyesters formed from reactants including cycloaliphaticpolycarboxylic acids and cycloaliphatic polyols. In a preferredembodiment, the cycloaliphatic group is formed from a 1,4 cyclohexanediacid and/or a compound containing a 1,4 cyclohexane diacid.

The PU polymer may include one or more cycloaliphatic groupsincorporated into the PU polymer through an isocyanate compoundcontaining a cycloaliphatic group. In such embodiments, the PU polymerpreferably contains cycloaliphatic groups incorporated through bothcycloaliphatic isocyanate and non-isocyanate compounds (e.g., compoundshaving the above X—Z—X structure).

Preferably, the cycloaliphatic groups having the X—Z—X structure areincorporated into a backbone of the PU polymer such that eachcycloaliphatic group is attached to the backbone through one or both ofthe X groups, thereby forming a segment of the backbone. In suchembodiments, the cycloaliphatic groups may be segments located at aterminal end of the backbone, intermediate segments located at anintermediate location of the backbone, or combinations thereof. In someembodiments, Z is a divalent cycolaliphatic ring structure and each X isa linkage group that attaches Z (and thus the cycloaliphatic group) toother portions of the PU polymer. In some embodiments (e.g., where oneof the X groups is hydrogen), the X—Z—X structure may be located at aterminal end of the PU polymer backbone.

The amount of cycloaliphatic groups in the PU polymer may vary dependingon the desired film or coating properties. Preferably, the amount ofcycloaliphatic groups in the PU polymer is optimized so that filmsformed from coating compositions containing the PU polymer exhibit bothsuitable levels of flexibility and hardness for the desired coatingapplications. As discussed above, preferably at least a substantialportion (and in some embodiments all) of the cycloaliphatic groups ofthe PU polymer is provided by compounds containing the X—Z—X structure.In some embodiments, the PU polymer includes at least about 3,preferably at least about 4, and more preferably at least about 5 weightpercent of cycloaliphatic-groups-containing containing the X—Z—Xstructure, based on the dry weight of the PU polymer. In someembodiments, the PU polymer includes less than about 20, preferably lessthan about 16, and more preferably less than about 12 weight percent ofcycloaliphatic groups containing the X—Z—X structure, based on the dryweight of the PU polymer.

A variety of isocyanates may be used to form the urethane linkagescontained in the PU polymer. In the embodiments in which the PU polymeris formed with PU prepolymers, the isocyantes may form terminal orpendant isocyanate groups in the PU prepolymers, which may then bereacted to form the urethane linkages. Suitable isocyanates includealiphatic, cycloaliphatic, araliphatic or aromatic isocyanates,diisocyanates, triisocyanates, or other polyisocyanates. Examples ofsuitable diisocyanates include 1,2-ethylene diisocyanate,1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate,2,2,4-trimethyl-1,6-hexmethylene diisocyanate,2,4,4-trimethyl-1,6-hexmethylene diisocyanate, 1,12-dodecanediisocyanate, cyclobutane 1,3-diisocyanate, cyclohexane1,3-diisocyanate, cyclohexane-1,4-diisocyanate,bis(4isocyanatocyclohexyl)-methane (Des W),1-methylcyclohexane-2,2-diisocyanate,1-methylcyclohexane-2,6-diisocyanate,3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl isocyanate (isophoronediisocyanate, IPDI),2,5-bis(isocyanatomethyl)-8-methyl-1,4,-methanodecahydronaphthalene,3,5-bis(isocyanatomethyl)-8-methyl-1,4,-methanodecahydronaphthalene,2,6-bis-(isocyanato)-4,7-methano-hexahydroindane, dicyclohexyl2,4′-diisocyanate, dicyclohexyl 4,4′-diisocyanate, 2,6-hexahydrotolylenediisocyanate, 2,6-hexahydro-tolylene diisocyanate,perhydro-2,4′-diphenylmethane diisocyanate,perhydro-4,4′-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate,1,4-phenylene diisocyanate, 4,4′-biphenyl diisocyanate,4,4′-diisocyanato-3,3′-dimethoxybiphenyl,4,4′-diisocyanato-3,3′-dimethylbiphenyl,3,3′-dipenylbiphenyl-4,4′-diisocyanate, 2,4′-diphenylmethanediisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), naphthylene1,5-diisocyanate, toluene diisocyanates (TDI), such as, for example,2,4-toluene diisocyanate, 2,6-toluene diisocyanate,N,N′-(4,4′-dimethyl-3,3′-diisocyanato-diphenyl)uretdione, m-xylylenediisocyanate, tetramethylxylylene diisocyanate, and the like; ortriisocyanates, such as, for example, 2,4,4′-triisocyanatodiphenylether, 4,4′,4″-triisocyanatotriphenylmethane,tris(4-isocyanatophenyl)thiophosphate, and the like; polyisocyanates(isocyanurates) based on 1,6-hexamethylene diisocyanate such as, forexample, 1,3,5-tris-(6-isocyanato-hexyl)-[1,3,5]triazinane-2,4,6-trione(Desmodur N-3300) and1,3-bis-(6-isocyanato-hexyl)-1-[(6-isocyanato-hexylamino)-oxomethyl]-urea(Desmodur N-75); or mixtures thereof. More preferred isocyanates includetoluene diisocyanates such as, for example, 2,4-toluene diisocyanate,and 2,6-toluene diisocyanate, 1,6-hexamethylene diisocyanate,2,4′-disocyanato-diphenylmethane, 4,4′-disocyanato-diphenylmethane,4,4′-diphenylmethane diisocyanate (MDI),3-isocyanato-methyl-3,5,5-trimethyl-cyclohexyl isocyanate (IPDI), bis(4isocyanatocyclo-hexyl)-methane (Des W), dicyclohexyl 2,4′-diisocyanate,dicyclohexyl 4,4′-diisocyanate; or mixtures thereof. Most preferredisocyanates are 2,4-toluene diisocyanate, and 2,6-toluene diisocyanate,1,6-hexamethylene diisocyanate, 2,4′-disocyanato-diphenylmethane,4,4′-disocyanato-diphenylmethane, 4,4′-diphenylmethane diisocyanate(MDI), 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl isocyanate (IPDI),bis(4isocyanatocyclohexyl)-methane (Des W), or mixtures thereof.

In some embodiments, the PU polymer preferably includes a plurality ofurethane linkages arising from at least about 15, more preferably atleast about 25, and even more preferably at least about 30 weightpercent isocyanates, based on the dry weight of the PU polymer. In someembodiments, the PU polymer includes a plurality of urethane linkagesarising from preferably less than about 55, more preferably less thanabout 50, and even more preferably less than about 45 weight percentisocyanates, based on the dry weight of the PU polymer. In addition tourethane linkages, the PU polymer may contain any other suitable linkagegroup (e.g., ester groups, ether groups, urea groups, amide groups,carbonate groups, and combinations thereof).

Preferably at least one of the reactants for forming the PU polymerincludes one or more air-curable ethylenically-unsaturated groups tofacilitate air-induced curing of coating compositions including the PUpolymer. Such ethylenic unsaturation may be introduced into the PUpolymer, for example, through incorporation of an ester polyol, ahydroxy-functional oil or fatty acid containing autooxidativecarbon-carbon double bonds, alkyd-based polyols, fatty amines, or anyother suitable reactant. The degree of saturation or unsaturation of thePU polymer may be tailored to facilitate crosslinking of coatingcompositions for various applications.

The PU polymer preferably contains at least about 5, more preferably atleast about 15, even more preferably at least about 20, and mostpreferably at least about 25 weight percent of ethylenically-unsaturatedgroups, based on the dry weight of the PU polymer. In some of theseembodiments, the PU polymer may contain less than about 65, preferablyless than about 55, and more preferably less than about 50 weightpercent of ethylenically-unsaturated groups, based on the dry weight ofthe PU polymer.

The cycloaliphatic groups and the air-curable ethylenically unsaturatedgroups preferably constitute at least about 30 weight percent and morepreferably at least about 25 weight percent of the PU polymer, based onthe dry weight of the PU polymer. While not wishing to be bound bytheory, it is believed that these concentrations allow the resultingcoating to exhibit good balance of flexibility and hardness, goodadhesion to a substrate, and good chemical resistance. In some of theseembodiments, the PU polymer preferably includes at least about 4 weightpercent of the cycloaliphatic groups and at least about 15 weightpercent of the air-curable ethylenically unsaturated groups.

In some embodiments, one or both of the cycloaliphatic groups and theair-curable ethylenically unsaturated groups may be provided in one ormore alkyd-based polyols. In these embodiments, the PU polymerpreferably contains at least about 20, more preferably at least about30, and even more preferably at least about 35 weight percent of groupsformed from alkyd-based polyols, based on the dry weight of the PUpolymer. In some of these embodiments, the PU polymer preferablycontains less than about 65, more preferably less than about 55, andeven more preferably less than about 50 weight percent of groups formedfrom alkyd-based polyols, based on the dry weight of the PU polymer.

Alkyd-based polyols (or hydroxy-functional alkyds) can be prepared usingany suitable method, and may or may not contain sulfonate functionality.Processes for producing alkyds from conventional oils are known in theart. See, for example, U.S. Pat. Nos. 4,133,786, 4,517,322, and6,946,509. An example of a method to prepare an alkyd could include thealcoholysis of an oil and polyol with a further reaction with polybasicacids and, optionally, further polyols. In addition, polybasic acids andfatty acids may be reacted with polyols in suitable proportions toprepare the alkyds. In a preferred embodiment, ethylenically unsaturatedgroups are incorporated into the PU polymer through acycloaliphatic-based alkyd polyol compound containing at least oneethylenically unsaturated group. Monoglycerides and diglycerides mayalso be utilized in place of, or in addition to, the hydroxy functionalalkyd. Suitable monoglycerides and diglycerides can be readilysynthesized using conventional techniques. Polyols synthesized via thereaction of at least one fatty acid and a polyol may also be employed toprovide ethylenic unsaturation.

Examples of suitable oils and/or fatty acids derived therefrom useful inproducing alkyds include compounds such as, for example, linseed oil,safflower oil, tall oil, cotton seed oil, ground nut oil, tung oil, woodoil, ricinene oil, sunflower oil, soya oil, castor oil, dehydratedcastor oil and the like. Examples of suitable fatty acids include soyafatty acids, linseed fatty acids, dehydrated castor fatty acids,linolenic fatty acids, ricinoleic fatty acids, and linoleic fatty acids.These oils or fatty acids can be used alone or as a mixture of one ormore of the oils or fatty acids.

Examples of suitable polyols for use in forming alkyds includedifunctional alcohols, trifunctional alcohols (e.g., glycerine,trimethylol propane, trimethylol ethane, trimethylol butane, trishydroxyethyl isocyanurate, etc.), tetrahydric or higher alcohols (e.g.,pentaerythritol, diglycerol, etc.), and combinations thereof. Examplesof suitable diols include neopentyl glycol (NPG), ethylene glycol,propylene glycol, diethylene glycol, triethylene glycol, tetraethyleneglycol, pentaethylene glycol, hexaethylene glycol, heptaethylene glycol,octaethylene glycol, nonaethylene glycol, decaethylene glycol,1,3-propanediol, 2,4-dimethyl-2-ethyl-hexane-1,3-diol,2,2-dimethyl-1,2-propanediol, 2-ethyl-2-butyl-1,3-propanediol,2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 2,2,4-tetramethyl-1,6-hexanediol,thiodiethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentanediol,2,2,4-tetramethyl-1,3-cyclobutanediol, p-xylenediol, hydroxypivalylhydroxypivalate, 1,10-decanediol, hydrogenated bisphenol A, andcombinations thereof. Preferred polyols include glycerol,trimethylolpropane, neopentyl glycol, diethylene glycol,pentaerythritol, and combinations thereof.

The PU polymer also preferably includes one or more groups derived fromaliphatic, cycloaliphatic, or aromatic polycarboxylic acids. As usedherein, the term “polycarboxylic acid” includes both polycarboxylicacids and anhydrides thereof. Examples of suitable polycarboxylic acidsinclude compounds such as, for example, aliphatic, cycloaliphaticsaturated or unsaturated and/or aromatic polybasic carboxylic acids,such as, for example, dicarboxylic, tricarboxylic and tetracarboxylicacids. Specific examples of suitable polycarboxylic acids includephthalic acid, isophthalic acid, adipic acid, terephthalic acid,tetrahydrophthalic acid, naphthalene dicarboxylic acid,hexahydrophthalic acid, endomethylenetetrahydrophthalic acid, succinicacid, glutaric acid, sebacic acid, azelaic acid, trimellitic acid,pyromellitic acid, fumaric acid, maleic acid, 1,4 cyclohexane diacid,hydrogenated phthalic anhydride, and anhydrides and combinationsthereof.

In some embodiments, polyols such as polyether polyols, polyesterpolyols, polyurea polyols, polyamide polyols, polycarbonate polyols, andcombinations thereof may be included in the PU polymer. In someembodiments, these compounds may include as constituents the polyolsand/or polycarboxylic acids described above in regards to alkydformation.

The PU polymer preferably contains a suitable amount of salt-containingand/or salt-forming groups to facilitate preparation of a PU dispersionwith an aqueous carrier. Examples of suitable salt-forming groupsinclude neutralizable groups (e.g., acidic or basic groups). At least aportion of the salt-forming groups may be neutralized to form saltgroups useful for dispersing the PU polymer into an aqueous carrier.Acidic or basic salt-forming groups may be introduced into the PUpolymer by any suitable method. One or more compounds containing anactive hydrogen group and active acid or base group may be included asreactants for forming the PU polymer. Examples of suitable compoundshaving active hydrogen and acid groups include hydroxy and mercaptocarboxylic acids, aminocarboxylic acids, aminohydroxy carboxylic acids,sulfonic acids, hydroxy sulfonic acids, aminosulfonic acids, andcombinations thereof. Examples of suitable compounds having activehydrogen and basic groups include aliphatic, cycloaliphatic andheterocyclic amino alcohols, diols and triols, amines, diamines,triamines, tetramines, amides, and combinations thereof.

For example, PU polymers can be made water-dispersible by incorporatingamine or acid functionality into the PU polymers. For example,water-based anionically stabilized PU polymers can be prepared byreacting polyols and dihydroxy carboxylic acid compounds (e.g.,dimethylol propionic acid and/or dimethylol butanoic acid) with anexcess of diisocyanate to provide a carboxylic acid functional polymerhaving NCO terminal groups. The acid groups can be neutralized withtertiary amines to provide salt groups. The resulting neutralizedpolymer can be readily dispersed in water. Alternatively, the anionicstabilizing group of the water-dispersible PU polymers can be replacedwith cationic stabilizing groups or non-ionic stabilizing groups, tofacilitate water dispersibility.

Any acid or base may be used to neutralize the acidic or basicsalt-forming groups and form salt groups. Examples of suitableneutralizing bases include inorganic bases such as sodium hydroxide,potassium hydroxide, lithium hydroxide, ammonia, triethylamine, dimethylethanol amine, and combinations thereof. Examples of suitableneutralizing acids include organic acids such as formic acid and aceticacid, inorganic acids such as hydrochloric acid and sulfuric acid, andcombinations thereof.

In some embodiments, inclusion of a salt-containing group may enable thePU prepolymer to be suitably dispersed in an aqueous carrier withoutrequiring a neutralization step. Examples of suitable salt-containinggroups include sulfonate groups present in the form of alkali metalsalts (e.g., lithium, sodium, potassium, etc.); sulfonate groups presentin the form of ammonium, tertiary amine, copper, or iron salts; andcombinations thereof. Examples of preferred monomers having sulfonategroups that may be incorporated into the PU polymer include,5-(sodiosulfo)isophthalic acid (SSIPA), 5-(lithiosulfo)isophthalic acid(LSIPA) and the like. Non-sulfonate salt-containing groups may also beemployed in addition to, or in place of, sulfonate groups.

The water-dispersible PU polymer may be formed using techniques andequipment that will be familiar to persons skilled in the art. Forexample, in the embodiments in which the PU polymers are formed with PUprepolymers, the PU prepolymers may be dispersed into an aqueous carrierand chain extended (or otherwise modified) to obtain higher molecularweight PU polymers. Extension of the PU prepolymers may be achieved byreaction of the neutralized water-dispersed PU prepolymers with one ormore chain extenders. This may occur, for example, by reacting one ormore chain extenders with terminal or pendant isocyanate(s) present onthe PU prepolymer. Examples of suitable chain extenders include alkylamino alcohols, cycloalkyl amino alcohols, heterocyclic amino alcohols,polyamines (e.g., ethylene diamine, diethylene triamine, triethylenetetra amine, melamine, etc.), hydrazine, substituted hydrazine,hydrazide, amides, amides, water, other suitable compounds having activehydrogen groups, and combinations thereof.

The above-discussed suitable dry weight concentrations of the compoundsin the PU polymer may be obtained by combined comparable concentrationsof the reaction components to form the PU prepolymer and/or polymer. Forexample, the PU polymer may contain at least about 4 weight percent ofcycloaliphatic groups (based on the dry weight of the PU polymer) byincluding at least about 4 weight percent of thecycloaliphatic-group-containing compound in the reaction components,based on the dry weight of the reaction components. Similarly, the PUpolymer may contain at least about 15 weight percent ofethylenically-unsaturated groups (based on the dry weight of the PUpolymer) by including at least about 15 weight percent of theethylenically-unsaturated compound in the reaction components, based onthe dry weight of the reaction components. As understood by personsskilled in the art, the concentrations of the compounds in the resultingPU polymer may be less than the concentrations in the reactioncomponents (e.g., within a few weight percent) due to partial reactionconversions, by-product formations, and the like.

The molecular weight of PU polymers of the present invention may varywidely and may be tailored for particular applications. In someembodiments, the PU polymers preferably have peak molecular weights (Mp)of at least about 3,000, more preferably at least about 5,000, and evenmore preferably at least about 10,000. In some embodiments, the PUpolymers preferably have Mp of less than about 150,000, more preferablyless than about 120,000, and even more preferably less than about100,000. Mp of a PU polymer, as defined herein, is the peak valueobtained from a molecular weight distribution plot, which has weightfraction on ordinate (Y-axis) and specific molecular weight on abscissa(X-axis). Weight fraction is defined as a ratio of PU polymer of aspecific molecular weight in a PU polymer sample to the total weight ofthe sample. For further discussion of Mp and methods for determining MP,see U.S. Pat. No. 5,534,310 Rokowski et al.

In some embodiments, the PU polymers preferably have number averagemolecular weights (Mn) of at least about 1,000, more preferably at leastabout 1,500, and even more preferably at least about 2,000. In someembodiments, the PU polymers preferably have Mn of less than about150,000, more preferably less than about 120,000, and even morepreferably less than about 100,000.

The ratio of cycloaliphatic groups included in the PU polymer relativeto the isocyanate units (or urethane linkages) included in the PUpolymer may vary to produce the desired result. The PU polymerpreferably includes less than about 8, more preferably less than about7, even more preferably less than about 6, and most preferably less thanabout 5 isocyanate units per 1 cycloaliphatic group having the X—Z—Xstructure. Moreover, the PU polymer preferably includes at least about1, more preferably at least about 2, and even more preferably at leastabout 3 isocyanate units per 1 cycloaliphatic group having the X—Z—Xstructure described above.

PU polymers of the present invention may exhibit any suitable acidnumber. Acid numbers are typically expressed as milligrams of KOHrequired to titrate a sample to a specified end point. Methods fordetermining acid numbers are well known in the art. See, for example,ASTM D 974-04 entitled “Standard Test Method for Acid and Base Number byColor-Indicator Titration” and available from the American Society forTesting and Materials International of West Conshohocken, Pa. In someembodiments, the PU polymer may have an acid number of at least about 2,and more preferably at least about 5. In some embodiments, the PUpolymer may have an acid number of less than about 40, and morepreferably less than about 30.

The PU polymer dispersion may be combined with additional additives andsolvents to form a coating composition. Such coating compositions may beformed using techniques and compositional ingredients that will befamiliar to persons skilled in the art.

Coating compositions of the present invention may contain one or morepigments. Suitable pigments include titanium dioxide white, carbonblack, lampblack, black iron oxide, red iron oxide, yellow iron oxide,brown iron oxide (a blend of red and yellow oxide with black),phthalocyanine green, phthalocyanine blue, organic reds (such asnaphthol red, quinacridone red and toulidine red), quinacridone magenta,quinacridone violet, DNA orange, and/or organic yellows (such as Hansayellow), and combinations thereof.

Coating compositions (or dispersions) of the present invention mayinclude driers. Typical driers include, for example, metal salts ofcobalt, manganese, lead, zirconium, calcium, cerium, lanthanum,neodymium salts, and combinations thereof. In some embodiments, metaldriers may be used in combination with accelerators such as, forexample, 1,10 phenanthroline, bipyridine, and the like.

PU coating compositions of the present invention can also include otheringredients such as plasticizers, colorants, dyes, surfactants,thickeners, heat stabilizers, leveling agents, anti-cratering agents,fillers, sedimentation inhibitors, ultraviolet-light absorbers, and thelike to modify properties. Additives such as heat stabilizers,ultraviolet-light absorbers, etc., can be dispersed in the reactionmixture and become an integral part of the urethane polymer.Alternatively, the additives may be added after the water-dispersible PUcompositions (or dispersions) have been formed.

In some embodiments, PU coating compositions or dispersions of thepresent invention preferably include less than about 30, more preferablyless than about 20, and even more preferably less than about 10 weightpercent VOCs, based on the total weight of the coating composition ordispersion.

A suitable polyurethane dispersion of the present invention may be madeby combining 32 to 50 parts of isocyanate, 35 to 55 parts of alkydpolyol containing the X—Z—X structure, and 4 to 12 parts of aliphaticdicarboxylic acid in a reactor. The choice of which isocyanate, alkydpolyol, and dicarboxylic acid to use and in what specific amount may bedetermined based on the desired end use. If desired, 0 to 30 parts otheradditives may be introduced. The reactants are reacted under a nitrogenblanket in the presence of a suitable amount of n-methylpyrollidone. Themixture is heated to 80° C. whereupon 200 parts-per-million (ppm)dibutyl tin dilaurate is added and the reaction is processed until theisocyanate level of the mixture is below about 5% as determined bytitration with hydrochloric acid.

The concentrations of the isocyanate and the alkyd polyol preferablyprovide excess amounts of isocyanate groups relative to the organichydroxyl groups of the alkyd polyol. In some embodiments, the reactioncomponents preferably include about 3 equivalents of isocyanate or less,more preferably about 2.5 equivalents of isocyanate or less, and mostpreferably about 2 equivalents of isocyanate or less per 1 equivalent oforganic hydroxyl group. In some of these embodiments, the reactioncomponents preferably includes at least about 1.2 equivalents ofisocyanate, more preferably at least about 1.4 equivalents ofisocyanate, and even more preferably at least about 1.5 equivalents ofisocyanate or less per 1 equivalent of organic hydroxyl group. Thisdesirably reduces the amount of remaining organic hydroxyl groups in theresulting PU prepolymer after the reaction. In some of theseembodiments, the PU prepolymer is at least substantially free of organichydroxyl groups after the reaction. Accordingly, the resulting PUprepolymer preferably includes at least about one terminal or pendantisocyanate group, and more preferably includes at least about twoisocyanate groups as terminal and/or pendant groups.

The resulting PU prepolymer is then cooled to about 65° C. and asuitable amount of triethylamine is added to form salts groups on the PUprepolymer. The PU prepolymer is then dispersed into 50° C. deionizedwater and is subsequently chain extended using 2 to 6 parts of polyaminechain extender. 35 ppm manganese drier is then added and the dispersionis reduced to 33% solids by weight with water. In some embodiments, thesalts groups may be formed on the PU prepolymer for neutralization priorto the chain extending to form the PU polymer. In other embodiments, thePU prepolymer may be chain extended to form the PU polymer prior to theformation of the salt groups for neutralization. Additionally, one ormore portions of the salt formation/neutralization reaction may coincidewith the chain extending reaction.

The above alkyd polyol may be formed from 10-25 partscycloaliphatic-containing compound of the X—Z—X structure, 40-70 partsfatty acids or oil, and 10-40 parts dicarboxylic acid and/or polyol. Thechoice of which cycloaliphatic-containing compound of the X—Z—Xstructure, which fatty acids or oil, and which dicarboxylic acid and/orpolyol to use and in what specific amount may be determined based on thedesired end use. The reaction mixture is slowly heated to 230° C. andstirred as water is removed. The mixture is heated and tested until atest sample has an acid number of less than 2 mg of KOH/gram. Once theacid number is less than 10 mg of KOH/gram, a suitable amount xylene isadded and the mixture processed under reflux. The xylene is stripped toless than about 1%.

Thus, as described above, the present invention provides awater-dispersible PU polymer that includes at least one cycloaliphaticgroup of the X—Z—X structure located preferably in a backbone of the PUpolymer. Relative to films formed using conventional water-dispersiblePU polymers, films formed using water-dispersible PU polymers of thepresent invention may (1) exhibit comparable or enhanced properties suchas hardness and flexibility and/or (2) utilize reduced amounts ofisocyanate.

EXAMPLES

The present invention is more particularly described in the followingexamples that are intended as an illustration only, since numerousmodifications and variations within the scope of the present inventionwill be apparent to those skilled in the art. Unless otherwise noted,all parts, percentages, and ratios reported in the following examplesare on a weight basis, and all reagents used in the examples wereobtained, or are available, from the chemical suppliers described below,or may be synthesized by conventional techniques.

A PU dispersion was prepared by combining a dihydroxy carboxylic acidcompound (dimethylol propionic acid), a polyester compound (neopentylglycol/adipic acid), an isocyanate compound (Desmodur W), an alkyd-basedpolyol, and n-methylpyrollidone solvent. The alkyd-based polyol wasderived from a cyclohexane compound (cyclohexane dicarboxylic acid)(having a structure X—Z—X), an ethylenically-unsaturated fatty acidcompound (soya fatty acids), and a tri-functional polyol (trimethylolpropane). The isocyanate compound was provided in an excess amountrelative to the isocyanate-reactive hydroxyl groups. Table 1 lists therelative concentrations of the reaction components, based on the dryweight of the reaction components.

TABLE 1 Component Percent by weight Dihydroxycarboxylic acid 6.0Alkyd-based polyol 45.7 Polyester 8.0 Isocyanate 40.3

The reaction components were heated to 80° C. whereupon dibutyl tindilaurate was added and the reaction was processed until substantiallyall of the isocyanate-reactive hydroxyl groups were reacted with theisocyanate compounds. The resulting PU prepolymer mixture was thencooled to about 65° C., thereby providing prepolymers having cyclohexanegroups, ethylenically-unsaturated groups, carboxylic acid salt-forminggroups, and terminal and/or pendant isocyanate groups. Because an excessamount of the isocyanate compound was used, the resulting prepolymerswere substantially free of isocyanate-reactive hydroxyl groups.

Triethylamine was then added to react with the carboxylic acid groups toform salts groups on the PU prepolymers. The PU prepolymers were thendispersed into chilled deionized water, and reacted with ethylenediamineto chain extend the PU prepolymers to form the PU polymer havingurethane linkages. Manganese drier was then added, and the PU polymerdispersion was adjusted to 33% solids.

The PU polymer dispersion was subsequently coated onto a substrate, anddried. The drying caused the ethylenically-unsaturated groups of the PUpolymer to crosslink, thereby strengthening the resulting coating. Thecombined concentrations of the cyclohexane groups (about 7 weightpercent) and the ethylenically-unsaturated fatty acid groups (about 26weight percent) in the PU polymer was greater than 30% by weight of thePU polymer, based on a dry weight of the PU polymer. As discussed above,this allowed the resulting coating to exhibit good balance offlexibility and hardness, good adhesion to the substrate, and goodchemical resistance.

Coatings prepared with the PU polymer dispersion of Example 1 were thencompared to the oil-modified urethane coatings of Comparative ExamplesA-C, where Comparative Example A was a coating commercially availableunder the trade designation “OLYMPIC” (product number 43884) from PPGArchitectural Finishes, Inc., Pittsburgh, Pa.; Comparative Example B wasa coating commercially available under the trade designation “MINWAX”(product number 71028) from Minwax Company, Upper Saddle River, N.J.;and Comparative Example C was a coating commercially available under thetrade designation “RUST-OLEUM” (product number 130001) from Rust-OleumCorporation, Vernon Hills, Ill. Table 2 lists the concentrations ofVOCs, the dry set-to-touch (STT) times, the dry tack-free (TF) times,and the dry through-dry (TD) times for the coatings of Example 1 andComparative Examples A-C.

TABLE 2 VOCs Examples (grams/liter) Dry STT Dry TF Dry TD Example 1 212<25 minutes <35 minutes 1.5 hours Comparative 444 1.25 hours 5.5 hours6.5 hours Example A Comparative 451 45 minutes 3.25 hours 4.5 hoursExample B Comparative 513 1 hour 2.25 hours 4.5 hours Example C

Dry times were determined on films applied by brush or pad to about 38dry micrometers (about 1.5 dry mils) to about 51 dry micrometers (about2.0 dry mils), on lacquer charts (Leneta Co. Form 8B) by both fingermethod and Gardner Drytime Recorder (Model DG-9602). As shown, thecoating of Example 1 contained a low concentration of VOCs, and wascapable of drying faster than the coatings of Comparative Examples A-C.

The coatings of Example 1 and Comparative Examples A-C were also testedfor abrasion resistance pursuant to ASTM D4060-01, and were run ondouble coated lacquer charts (Form 8B from Leneta Company, Inc., Mahwah,N.J.). Coupons were cut from each chart and conditioned to constantweight in a dessicator. Each coupon was then weighed before and afterthe abrasion test cycles to determine the amount of material lost due toabrasion. The coating of Example 1 exhibited a loss of 25 milligrams(mg), the coatings of Comparative Examples A and C each exhibited lossesof 13 milligrams, and the coating of Comparative Example B exhibited aloss of 19 milligrams. While the coating of Example 1 exhibited agreater loss compared to the coatings of Comparative Examples A-C, thecoatings of Comparative Examples A-C are commercially recognized fortheir good abrasion resistances. Accordingly, all of the tested coatingsexhibited low amounts of material loss, which corresponded to goodabrasion resistances.

The coatings of Example 1 and Comparative Example C were also tested forimpact resistance, heel marking, and scratch resistance. The impactresistance test was performed pursuant to ASTM D2794-93, and was run ondouble-coated maple flooring coated to about 38 dry micrometers (about1.5 dry mils) to about 51 dry micrometers (about 2.0 dry mils). Theimpact force applied was 14 kilogram-centimeters (12 pound-inches), andthe impact area was then evaluated under magnification for cracking ordelamination. After the test, each coating was substantially free ofcracking or delamination, thereby illustrating the good impactresistances of the coatings.

The heel marking test was performed on double-coated maple flooringcoated to about 38 dry micrometers (about 1.5 dry mils) to about 51 drymicrometers (about 2.0 dry mils). A rubber heel was rub across thecoated flooring at about a 45E angle until the rubber heel exhibitedobservable wear. The coated flooring were then wiped clean and visuallyexamined for damage to the coatings. Upon examination, neither coatingexhibited visual damage.

The scratch resistance test was performed pursuant to ASTM 5178-98, andeach coating passed an application of 800 grams. Accordingly, thecoating of Example 1 also exhibited similar physical resistances to thecoating of Comparative Example C, which is also commercially recognizedfor its good physical properties. In addition, the coating of Example 1was prepared from the PU polymer dispersion, which contained a lowconcentration of VOCs.

The coatings of Example 1 and Comparative Example C were also tested forchemical resistance by exposing each coating to different chemicalsubstances. For each coating, two coatings of the material were appliedonto a black vinyl chart (Leneta Co. Form P121-10N) to obtain a filmthickness of about 1.5 to 2.0 dry mils. Spots of each chemical substancewere then applied to each chart and covered with a watch glass for twohours. The chemical substances applied included a 20% aqueous vinegarsolution, an 80% aqueous isopropanol solution, a hand lotion (“SuaveSkin Therapy with Vitamin E and Lanolin” from Unilever United States,Inc., Englewood Cliffs, N.J.), a suntan lotion (“Banana Boat SunLotionwith Aloe” from Sun Pharmaceuticals Corporation, Westport, Conn.), and ashower cleaner (“Arm and Hammer Clean Shower” from Church & Dwight Co.,Inc., Princeton, N.J.).

The glasses were then removed, and applied chemical substances wereremoved with a soft, clean cloth. The films were then examined forsoftening, swelling, color, and any change in appearance. The films werethen rinsed with clean water, allowed to dry overnight, and re-evaluatedfor the same changes. Upon examination, the 20% aqueous vinegarsolution, the hand lotion, the suntan location, and the shower cleanerdid not cause any noticeable effects on either coating. With respect tothe 80% aqueous isopropanol solution, each coating was initiallysoftened, but recovered after allowing to dry overnight. Accordingly,the coatings exhibited good chemical resistances to the applied chemicalsubstances.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

The invention claimed is:
 1. A water-dispersible polyurethane polymer comprising: a plurality of urethane linkages; a plurality of cycloaliphatic groups derived from cycloaliphatic diacids; a plurality of salt or salt-forming groups; and a plurality of air-curable ethylenically unsaturated groups, wherein a combined concentration of the plurality of cycloaliphatic groups and the plurality of air-curable ethylenically unsaturated groups constitutes at least about 30 percent by weight of the polyurethane polymer, based on a total dry weight of the polyurethane polymer, and at least 20 percent by weight of the plurality of cycloaliphatic groups and the plurality of air-curable ethylenically unsaturated groups are provided by alkyd-based polyols, wherein the polyurethane is dispersible in water without requiring the use of a separate surfactant.
 2. The polyurethane polymer of claim 1, wherein at least one of the plurality of cycloaliphatic groups comprises a structure X—Z—X, and wherein: Z is an aliphatic ring structure; each X is a group independently selected from an ester group, an ether group, an amide group, a carbonate group, hydrogen, or CRn, where R is independently selected from hydrogen, a halogen, oxygen, nitrogen, an organic group, or a combination thereof and n is 0, 1 or 2; and at least one of the X groups is a divalent linkage group that attaches the at least one cycloaliphatic group to another portion of the polyurethane polymer.
 3. The polyurethane polymer of claim 2, wherein Z comprises a divalent aliphatic ring structure and the X groups comprise divalent linkage groups that attach the at least one cycloaliphatic group to other portions of the polymer.
 4. The polyurethane polymer of claim 1, wherein the plurality of cycloaliphatic groups are located on a backbone of the polyurethane polymer.
 5. The polyurethane polymer of claim 1, wherein the plurality of cycloaliphatic groups constitute at least about 4 percent by weight of the polyurethane polymer, based on the total dry weight of the polyurethane polymer.
 6. The polyurethane polymer of claim 1, wherein the plurality of air-curable ethylenically unsaturated groups constitute at least about 15 percent by weight of the polyurethane polymer, based on the total dry weight of the polyurethane polymer.
 7. The polyurethane polymer of claim 1, wherein a ratio of the plurality of urethane linkages to the plurality of cycloaliphatic groups in the polyurethane polymer includes less than about 8:1. 